Spend a little more and run some 4 conductor 10 gauge so you can have 230V and 30A. I built a 12x12 that is sheetrocked with linoleum floor for my reloading room and storage area. With the added power I have no problem running heaters, A/C, and a small compressor. More power is never a bad thing.

Even with a 20 amp circuit I'd guess that lights plus power tool(s) plus compressor kicking on is going to pop a breaker. I've never heard of the multiwire drop but it sounds like a great idea. You learn something every day...

Also, if you can't do a slab or permanent footings you could consider building on a prepared surface. Dig holes as deep as a footing and fill with tamped gravel/rock. Basically you want it to drain so you don't get frost heave. Then spread landscape fabric and more gravel over the full area, then build on blocks/pads. You need to tie the structure down to augured in anchors (like used for mobile homes) or something you bury when you dig the footings.

I'm not saying this is the best option but it can work if you can't place permanent footings. FYI, you should confirm that with the easement - can you put in permanent footings in your easement?

There are setback (from the property line) requirements in nearly every location, out here it is 10ft. An Easement is for like a powerline, utility lines, sewer etc. it is basically your property, but for the greater good, you give them rights to bury them or put in power poles etc.

__________________"Axeheads are supposed to be sharp, but you are one blunt tool."
FLynes

If you love wealth more than liberty,the tranquility of servitude more than the animating contest of freedom, go home from us in peace. We seek not your counsel nor your arms. Crouch down and lick the hand that feeds you. May your chains sit lightly on your shoulders and may posterity forget that you were our countrymen.
-Samual Adams

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Thomas Jefferson

"Your right, the Tea Party and the OWS are the same, just like the America Revolution and the French Revolution were the same. The only problem is the American Revolution ended with Liberty, Freedom, Justice for all and a shining light upon a hill. The French Revolution ended with lynchings, guillotines, murder and socialism. So yeah, I could see how one could confuse the two..."
Mac Wilson

Backfilling your footing holes with gravel instead of dirt is a good idea. You should still not dig it oversize so you shouldn't need much. Whatever you use do try to tamp down your backfill somewhat as it goes back in.

And full disclosure, I'm not a contractor that does this for a living so I'm happy to be corrected if necessary.

And +1 on the 230 amp circuit. The incremental cost would be small and it would remove any concerns about power. If you aren't planning on doing significant work out there it's probably overkill but the startup load of an electric motor can be quite large.